Hemangiosarcoma in Dogs: Is There Any Hope?

Hemangiosarcoma in dogs is a prevalent type of cancer, which affects them more than any other species. The dog breeds which are more prone to develop tumors from this category are: Boxers, English Setters, German Shepherds, Golden Retrievers, Great Danes, and Pointers.

The risks are also higher for male dogs which have an age between 6 to 10 years. However, some cases also appear in the female population as well as in younger dogs. In this article we’ll tell you everything you need to know about hemangiosarcoma, from causes and symptoms to diagnosis and possible treatments.

What is hemangiosarcoma?

The cells that line your dog’s blood vessels are called vascular endothelial cells. The tumor which affects at first the endothelium or in other words, the lining of the blood vessels, and then spreads throughout the blood vessels themselves is called hemangiosarcoma.

It’s important to note that these tumors are malignant. There is also the benign type of tumors which affect the vascular endothelial cells. These tumors are called hemangiomas, they are caused by direct and prolonged exposure to sunlight, and they don’t present a direct peril to your dog’s life. In fact, many people get hemangiomas as well.

On the other hand, when it comes to hemangiosarcoma, this is an almost dog-specific type of tumor, which people don’t get. The equivalent that could be attributed to human beings is called angiosarcoma, but less than 1% of the people with cancer develop this particular tumor. The ones who do mainly get infected with dangerous chemical substances from their workplace, or receive some type of radiation treatment for other forms of cancer.

Although it’s assumed that this disease affects almost 2 million dogs in the US annually, doctors don’t know all that much about it and they consider it a pretty challenging illness to deal with. The experiments that have been done to lab rats show that they develop hemangiosarcoma if they present a certain chromosomal mutation, but it’s not yet established if that’s also the case for dogs.

What causes it?

There is no simple answer to this question because basically the causes are unknown. There are however, some scientific assumptions on what could determine these type of tumors to appear in dogs. We’ll analyze them below.

Genetic factors

One of the reasons why it’s believed that hemangiosarcoma can be caused by heredity is that it’s a tumor that occurs almost exclusively in dogs. As such, breeding or genetics are important risk factors. However, it’s how they are modeled by the environment that counts the most in developing these mutations.

As a matter a fact, the interactions between genetics and environment can be best described like this: the cells mutate because of heredity, and these mutations affect your dog’s cells in two ways: they mess with their growth process and they also cause lesions to those cells.

But why do these tumors occur? Well, the cells in your dog’s body divide at a constant pace to replace older or damaged cells, and they’re controlled by enzymes. Since these enzymes are not infallible, that means that as a mutated cell continues to divide, it will introduce new mutations into your dog’s body, and that’s how a tumor appears.

However, it’s important to notice that mutation does not equal cancer. In reality, your dog may have a certain mutation in his body without actually being diagnosed with cancer. As such, the mutation is just a risk factor to be taken into consideration.

Stem cells

Stem cells got a lot of media attention as of late, because they’re deemed a panacea. However, recent research suggests that they may be the only cells in our bodies – or in your dog’s body for that matter – which cause cancer. The mutation through division theory we’ve discussed above is now challenged by a new hypothesis, which entertains the assumption that this division of mutated cells isn’t without an end.

Actually, it aims to prove that the mutation-inducing cells’ population is limited just to the cancer stem cells. These cells are able both to renew themselves and to produce new cells of different types and functions.

As such, a few stem cells in a tumor that can renew themselves and make other types of cells as well, are the ones which generate the big mass of a tumor. If secondary mutations develop with a lot of different type of cells in them, then they’ll become aggressive tumors. Otherwise, they’ll be low-grade and called indolent tumors.

If we’re to accept this theory on cancer, it may very well be that we get a more complete explanation as to why the dogs develop hemangiosarcoma later in their lives and not much earlier: it’s because just a few stem cells have the capacity to give rise to a tumor. On the other hand, the probability for any given dog to develop cancer is still staggeringly high.

Another good thing that could come out of this scientific model, if it turns out to be true, is that the actual therapies can be better targeted to the stem cells, to treat the hemangiosarcoma with more success and even with less toxic therapies.

What are the most common types?

There are four more common types of hemangiosarcoma:

Dermal – located on the skin.

Hypodermal – located under the skin.

Visceral – located on the spleen, liver, pericardium, and heart.

Mesenchymal – located on the lymphatic and circulatory systems, as well as on the connective tissues throughout the dog’s body, such as bone and cartilage

There are also other sites where this tumor can develop: the right atrium, lungs, kidneys, mouth, muscles, bones, urinary bladder, left ventricle, uterus and retroperitoneum. When it comes to the incidence of each of the above types, the dermal and hypodermal hemangiosarcomas are responsible for only about 3% of the total cases, the liver tumors occur in 5% of the cases, while the spleen’s hemangiosarcomas are noticed in 50% of the cases. Mesenchymal tumors occur in 12% to 21% of all the cases.

Apart from being the most frequently seen, they’re also the most dangerous, because they go undetected for very long and then they prove deadly. Hemangiosarcoma gets filled with blood fast until they rupture and produce massive hemorrhage, fainting and death. Unfortunately, most dog owners don’t realize their dogs are sick until this last point in the tumor’s evolution.

What are the symptoms?

The problem with hemangiosarcoma is that it’s rarely detected in time. In fact, most cases show a time period of about two months from the discovery of some worrying symptoms to the actual death of the dog exhibiting them after surgery.

As such, it’s wiser to take your dog to the vet for regular consults and blood tests, because early detection is how you can increase his chances of survival.

Apart from this, there are some signs which may put you on the guard that something’s up. If you notice a red or black growth on hairless portions of your dog’s body, like his belly, that may be a type of hemangiosarcoma found on the skin.

Otherwise, further symptoms include:

Weight loss

Weakness

Lameness

Intermittent collapse

Rapid heartbeat (tachycardia)

Muscle incoordination (ataxia)

Seizures

Palpable abdominal mass

Dementia

Pale mucous membranes

Abdominal (peritoneal) fluid

Partial loss of movement (paresis)

Acute blood loss (often fatal)

These symptoms are generally related to visceral hemangiosarcoma, which affects the internal organs. Since it can spread anywhere from your dog’s spleen to his other internal organs, the symptoms can be more easily grasped.

Consequently, when a dog or a human is battling with any type of cancer, their body will try to starve the “enemy”, and that’s why you’ll notice a lack of appetite in your dog as well as a potential weight loss.

An incipient tumor can also lead to weakness as a sign that something’s wrong, but if that tumor is more developed it can even lead to collapses. In fact, that’s even more likely if the hemangiosarcoma has reached your dog’s lungs or brain. If he can’t breathe properly because his lungs are affected, then he can’t be on his feet for long.

If the tumor has reached his brain, you may notice a partial paralysis called paresis, or even ataxia (inability to coordinate muscles), as well as a few seizures. Your dog can also show signs of confusion and even dementia. Because he’s losing brain cells rapidly, he’ll forget stuff, be constantly anxious and nervous, maybe even become incontinent.

You’ll notice lameness as well if your dog’s brain is affected, but you can also see him limping because his bones are damaged. If he’s in huge pain, he may also not be able to move properly.

If your dog is losing blood because of the cancer, and if his organs aren’t functioning as they should, you may also notice that his heart will start beating faster in an effort to pump blood more efficiently. That is called tachycardia. Moreover, anemia caused by acute blood loss can be noticed from his pale mucous membranes. If the lining of his nostrils, lips and ears are whiter than usual, that’s a sure sign of anemia in your dog.

More to the point, if you touch his belly and feel it very full, that may be a sign of abdominal fluid gathering there, or even an abdominal mass, which may indicate cancer.

There are other types of symptoms as well, like an impaired spleen function if the tumor is located in the spleen, or an impaired liver function if it’s positioned in the liver. In the first case scenario, your dog’s immune system will be affected more, you’ll see your dog getting sick more easily, maybe even being more prone to intestinal parasites, but a rise in his red blood cells can also be observed in his blood tests.

As for the second case, the liver’s job is to aid the digestion process, eliminating the toxic substances from your dog’s body. As such, if you notice that your dog is feeling apathetic and has problems digesting the food, being bloated, constipated or diarrheic you can conclude there might be something wrong with his liver.

How is it diagnosed?

The diagnosis process requires your dog’s medical history and a detailed account of all the symptoms you’ve noticed so far.

That can tell doctors where the tumor is located and which body parts it affects.

Be prepared to answer these questions:

How is your dog’s appetite?

Has your dog recently lost weight?

Has your dog fainted?

Has your dog recently had seizures?

Is your dog more anxious or irritable than usual?

Is your dog less active?

Has your dog been experiencing incontinence?

Additionally, your vet will most likely have to conduct a series of tests, such as:

This can show if there are too many red blood cells and if there’s something wrong with the spleen.

Serum biochemistry. This test can indicate chronic hemorrhage, and also assess the liver function, by looking and the levels of protein, glucose, electrolytes and enzymes.

To see if your dog has any toxins in his urine or foreign skin fragments which show that his liver and kidneys aren’t working properly.

X-rays.These can tell your doctor if your dog has an abdominal mass or abdominal fluid.

Thoracic radiography. This will diagnose any presence of the tumor in your dog’s chest.

This technique can reveal the presence of tumors in the spleen or in the liver.

If your dog has signs of fluid accumulating near his heart, this will reveal a possible tumor in his heart.

This is used for a biopsy. The doctor will insert a fine needle in the tumor and extract some tissue to further analyze it, to see what type it is, if it’s malignant or not, and thus get a more reliable diagnosis.

What is the treatment?

If your doctor finds your dog suffers from hemangiosarcoma, depending how far along the cancer is and how much it has spread, the courses of treatment he may indicate to you are:

Surgery. This is the most aggressive option, during which your dog’s affected tissues will have to be removed, and in most cases the entire organ will have to be cut out, like in the case of most hemangiosarcomas of the spleen. During the surgery, the doctors will examine the entire abdomen. Afterwards, they’ll send samples of the collected tissue to be examined.
The basic problem with surgery is that it presents a high risk of irregular heart beats for your dog and he’ll have to be monitored after for up to 2 days. Sadly, a successful splenectomy gives your dog just about 3 more months to live.

Chemotherapy. This procedure can be employed alongside surgery, and if the combination between the two is effective, it can give your dog more time to live, almost up to a year. Generally doctors strongly recommend chemotherapy after surgery with some intravenous medicine given for a period of 3 weeks. If the hemangiosarcoma is very advanced and can’t be successfully operated, then chemotherapy can reduce its severity and ameliorate the symptoms.

Radiotherapy. This form of treatment isn’t used very much at the moment, because hemangiosarcoma has a high metastatic rate and because it can be spread throughout your dog’s body. However, radiotherapy could be employed as a palliative measure, alongside chemotherapy especially for dermal hemangiosarcoma.

There are also some other forms of treatments associated with inpatient care, such as:

Intravenous fluids for dehydration.

Blood transfusions for severe anemia.

Coagulation management.

All that being said, hemangiosarcoma is a dreadful type of cancer both for you and your dog, and its negative strain on your lives don’t cease even after the surgery. As such, your dog will have to be kept away from strenuous activities. Besides this, he’ll also experience some pain, and you can give him medicine for that, but you’ll also have to be prepared to accommodate him indoors, even if he’s an outdoor dog. It’s also advisable not to take him out very often, not even for urinating or defecating.

Moreover, you’ll have to make some appointments for follow-up thoracic and abdominal radiographies, as well as abdominal ultrasounds so that the possibility of recurrence can be monitored and managed.

Following the proper recovery measures and indications given by your vet is very important for preventing the apparition of spontaneous hemorrhaging, as well as for improving your dog’s life expectation.

So is there any hope? The genes that determine hemangiosarcoma in certain breeds could be identified and eliminated. Thus, this terrible cancer could be eradicated, or at least diminished. However, for now the most important thing is for you to be there for your dog. Even if he’s ill, he can still feel your love.

Wyatt Robinson had a great 25-years career as a veterinarian in United Kingdom. He used to be a member of British Veterinary Association and worked in 3 pet hospitals in London and Manchester. He is shining when he sees his pets healthy and full of energy and it is his duty to help other dog owners to keep their best friends full of life.

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